I have a 12RES showing 114 volts on phase and 124 volts on phase 2. 240 v between phases. Is this typical?

thats the max output of the unit total

A one phase 3 wire system has a center tap. Two hots and a neutral. Typical 120/240 volts.
A three phase 4 wire system has Three hots in a Y or Delta. The Y system has three hots and the neutral comes from the center of the Y, this is the neutral and grounded conductor, 120 volts from hot to ground and 208 volts hot to hot. In a 3 phase system the voltage is not doubled hot to hot as in a single phase system because the hots are 120 degrees phased from each other and the square root of 3 is the factor, multiply the 120 volts by 1.73 to get 208 volts hot to hot. Multiply 208 by the reciprocal of 1.73 and get 120 volts. Your exact application is not given so it is not known. A delta system is a triangle and the angle of each triangle is a hot wire, one angle would be grounded or the center tap of one of the sides of the triangle. Y is the configuration of the windings of the alternator or transformer and Delta is the configuration as a triangle of the windings of the alternator or transformer where the power supply is.

With a three phase home service, you can only connect two hots from your single phase generator, and the neutral. One of the house's hot does not get connected and any three phase loads in the house should be switched off and kept from energyzing or a circuit breaker or fuse serving that 3 phase load may trip.
Only one power supply can be connected at a time. The power company power must not be connected at all while using an alternate power supply unless your power supply has means to synchronize the alternating cycle.

It is adviced that the loads be kept within 10% of their rated voltage, especially motors.

My limited research indicates this heater is designed for USA electrical systems. That would mean single phase, 240/208 volts, 60 Hz. The drawings I reviewed shows a 2 pole, 240 volt breaker feeding each heating circuit. That means no "neutral wire" goes to the heater and therefore no 120 volts is needed. This is good. Kenya's system is single phase, 240 volts, 50 Hz. The heater should work reasonably well on the African system. Connect the power just like you would in the US.

there is no motor that is single phase with 415 volts only 240 volt or 120volt and you cannot use a 3 phase motor on single phase it will just fail to start buzz and burn it up .single phase motors have capacitors 3 phase motors do not

What kind of diagram are you looking for? Large business and warehouses have 3 Phase. I've not heard of a house. but let me know. Typically 110 comes out of one breaker and one neutral wire (and saftey ground is 3rd) 220 comes out of two hot leads and one neutral wire (single phase). 3 phase comes out of 3 hot leads and one neutral but is still 220 volt.

HI:) If that is a 3 phase 440 volt and you want it to use 220 volt 1 Phase you will have to get a phase inverter to change it from a 3 phase to a single phase.

If the electrical 120 volt source is single phase, the only way to run this motor is with a single phase to three phase converter. Best to sell the three phase motor and obtain a similar horsepower 120 volt single-phase capacitor-start motor (1750 RPM) for the compressor. You would also require a 3-phase pressure switch for use with the 3-phase motor. Hope this helps!

You cannot wire a three phase motor for single phase and you cannot wire a single phase motor for three phase. If you have a three phase dual voltage motor your options are 220 or 440 volts. If you have a single phase dual voltage motor your options are 120 or 240 volts. A 208 volt Hobart motor will only function correctly on 208 volts and is not dual voltage.

That is a single phase hot water heater. Hope this helps